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Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM4PEPF00027A67.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAWPR08MB9805 X-Spam-Status: No, score=-0.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, FORGED_SPF_HELO, KAM_DMARC_NONE, RCVD_IN_BL_SPAMCOP_NET, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_PASS, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE, UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Luis Machado via Gdb Reply-To: Luis Machado Errors-To: gdb-bounces+public-inbox=simark.ca@sourceware.org Sender: "Gdb" Hi, On 12/20/23 09:42, Schimpe, Christina via Gdb wrote: > Hi all, > > I am writing to you to collect feedback for the name of a new command, we would > like to introduce. The command shall be used to print the shadow stack backtrace. > > A shadow stack is a second stack for a program introduced in the Intel (R) > Control-Flow Enforcement Technology (CET). The shadow stack is used for > control transfer operations to store the return addresses. > > This is an example command name and output for the shadow stack backtrace: > ~~~~ > (gdb) info shadow-stack bt > Address Symbol > #0 0x0000000000401131 call1 > #1 0x0000000000401145 main > #2 0x00007ffff7c3fe70 __libc_start_call_main > #3 0x00007ffff7c3ff20 __libc_start_main_impl > (gdb) set print symbol-filename on > (gdb) info shadow-stack bt > Address Symbol > #0 0x0000000000401131 call1 at amd64-shstk.c:51 > #1 0x0000000000401145 main at amd64-shstk.c:56 > #2 0x00007ffff7c3fe70 __libc_start_call_main > #3 0x00007ffff7c3ff20 __libc_start_main_impl > (gdb) help info shadow-stack bt > info shadow-stack backtrace, info shadow-stack bt > Print the entire backtrace of shadow stack, > or the innermost [COUNT | -COUNT] addresses for the current process. > To print the source filename and line number in the backtrace, > the "symbol-filename" option of the print command should be toggled on. > (See "show print symbol-filename") > ~~~ > > It is configurable using "print symbol-filename" and COUNT. > The command can be called by the following names: > - "info shadow-stack bt", "info shadow-stack backtrace" > >>>From my perspective, the command name has the following pros and cons: > (+) Easy to understand by just looking at the command name. > (-) Rather long syntax > > We also considered other command names such as > > - "info cet bt", "info cet backtrace" > (+) Short syntax possible > (-) Not so easy to understand by just looking at the command name. I miss the > name "shadow stack". > > - "info shstk bt", "info shstk backtrace" > (+) Short syntax possible > (-) "shstk" ist not an official abbreviation (in contrast to "cet"). "shstk" is > mostly used by the linux kernel and might not be known by the user. > > - "info shstk", "info shadow-stack" > (+) short syntax possible > (-) Without "backtrace" in the name, it might not be so easy to understand. > > Having in mind that that the shadow stack is not only a x86-specific feature > but can be seen as a generic concept we also considered that it could be > part of the existing backtrace command, e.g.: > - "bt -shadow" > (+) Short syntax > (+/-) Most of the settings of the bt command don't apply to the shadow > stack (frame arguments and info). This might cause confusion. > > For this option, it might make sense to introduce a new setting for the bt > command which is for shadow stack only, e.g. "-symbol-filename [on|off]". > > What are your thoughts on this topic? Any feedback and new ideas are welcome. I like the option of reusing whatever is possible to reuse from the current backtrace command, so "bt -shadow" seems like a sensible option. It doesn't seem to me like this command will be used a lot. I expect it will be useful only when we catch a fault due to a corrupt stack trace, so putting it within the more general "backtrace" option would accomplish that. With that said, depending on how shadow stack support is implemented in gdb, I expect gdb will automatically validate the stack trace against the shadow stack (maybe on a fault), and complain if they go out of sync. Does that sound reasonable? Maybe even display where the flow veered off course. AArch64 will have a counterpart of this, with the Guarded Control Stack (GCS) feature, so the more generic we make this, the better.